Electric discharge-tube system



' Nov. 26, 1929.

P. R. DIJKSTERHUIS 1,737,224-

ELECTRIC DISCHARGE TUBE SYSTEM Filed Jan. 1925 Patented Nov. 26, 1929 UNITED STATES PATENT {OFFICE POPKO nnmnnn nIJxsTEnnUIs, on nmnnovnn, NETHERLANDS, nssronon no N. v. rnrurs' GLOEILAMPENFABRIEKEN, or nmnnovnn, nnzrnnnnnnns ELECTRIC DISCHARGE-TUBE SYSTEM Application filed January 7, 1925, Serial No. 1,072, and intake Netherlands February 9, 1924.

This invention relates to an installation for operating an electric discharge tube comprising an'incandescent cathode, an anode, a controlling grid, and aso-called foregrid.

A foregrid is to be understood to mean an auxiliary electrode having some apertures and arranged between the cathode and the to connect the installation for operating such a discharge tube so as to be suitable for generating, receiving,or amplifying electric oscillations without making use of a retroaction coil.

In the known retroaction circuit-arrangements, which for example are utilized in triodes, there are used for the connection of the anode-circuit to the grid-circuit two separate coils wound in opposite directions or a single coil. In the latter case the anode and the grid areeach connected to one of the ends of the saidcoil while the cathode is connected to an interjacent point of the coil.

It is not possible to arrange a single coil to belong to the, grid circuit as well as to the anode circuit because the anode current fluc+- shows diagrammatically the construction of an installation, according to the invention, which is particularly suitable for amplifying oscillations "of low frequency. Figure 2 shows the current-voltage characteristics of.v the circuit. 1

In Figure 2 of the accompanying drawing the foregrid current 6 and the anode current 2', are set out as a function of the controlling grid tension c while the anodeand the foregrid tension are kept constant in this case. It appears that in a given interval (between the points C and D) of the controlling grid-tension the anode current '5, decreases when the grid tension decreases, while in the same region the foregrid current 5,; increases.

This property isutilized in order to obtain an installation-comprising a circuit in which a negative resistance occurs.

For this purpose an ohmic resistance is provided which pertains toiboth the current circuits formed betweenthe incandescent cathode and the controlling gri'drand between the incandescent cathode and the foregrid. In

this case the foregrid has preferably substantially the same potential as the anode.

According to the invention one end of the resistance is electrically connected to the incandescent cathode whereas the other end is electrically connected to the foregrid and through a battery to the controlling grid.

The resistance is preferably non-inductive tuations have the Same Phase as the fitand is adjustable so that the voltage applied or voltage variations at the grid (that is to say :The anode current increases as the grid. tension increases and vice versa) In discharge tubes comprising a foregrid which has a positive potential relative to the v cathode, preferably a potential correspondving to that, of the anode, the anode current fluctuationsare in a certain region in phase Wlth the tension or voltage fluctuations at the-grid. The foregrid current fluctuations 5 are however in v opposite'phase therewith,

that is to say; If the tensionof'the controlling. grid' decreasesthe' foregrid current in creases, and '-conversely The tensions at the anode, and, the for egri d are in this case supposed to be constant.

Eto the control grid and the foregrid maybe varied. It is also advantageous to provide batteries for the anode and foregrid such that. the potential applied by either or both tothe respective electrodes my be varied.

With the aid of Figure 1 it is easyto see that a circuit can be indicated in which a negative resistance occurs.

The electric discharge tube shown in Figure 1 consists of an envelopev 1 of glass or similar material, in whichanincandescent cathode 2, a foregrid 3, a' controlling grid 4, and an anode 5 are arranged. p p L The envelope 1 maybe exh: usted to a high degree or may contain a suitable gaseous fill I In, thevaccornpanying drawings, Figure 1 ingat-low pressure; may forexample be filled with a rare gas, preferably with argon having a pressure of 100 microns or less.

The incandescent cathode 2 is heated to the required temperature by a battery 6 while the anode circuit is provided with a battery 11 and a telephone 12. The foregrid 3 is likewise -connected to the battery 11 with the interposition of a regulable resistance 10 and the controlling grid 4 s connected to the resistance 10 via a-secondary coil 8 of a transformer 8,

'9 and a battery 7 having a tension which is equal to or a little higher than that of the battery 11.

It will be noticed that the resistance 10 pertains to the foregrid circuit as well as to the controlling grid circuit while the resistance is electrically connected to the incandescent cathode and to the two grids.

, It has now been found that a current tension characteristic measured for example between the points P and Q of the opened gridcircuit has a dropping character so that the resistance between the points P and Q is a negative one. This may be seen from the following:

If at a constant tension or voltage of the controlling grid 4),; the tension c of the foregrid is increased, the current z' flowing to- ;vards the foregrid will increase; consequent- If on the contrary v is increased and u is kept constant, the current a}; flowing to the foregrid will decrease, for if the potential of the controlling grid becomes more positive, the anode current will increase, owing to which electrons which at a smaller tension vwould move towards the foregrid are deflected to the anode. The anode takes therefore more current at the cost of the foregrid so that the current flowing to this grid decreases. Consequently Furthermore a tension fluctuation at the con- [trolling grid will cause an equally great ten- .fii sion fluctuation at the feregrid and conse- .quently,.too,- at the point P. To the QD O fluctuation dV at the point P there applies consequently and consequently:

In order that there be a negative resistance between the points P and Q it is necessary that In general this condition is satisfied and there is consequently a negative resistance between the points P and .Q.

Thevalue of the resistance 10 is substantially equal to the absolute value of the negative resistance in the circuits which is common to the two grids so that the total resistance in, this circuit approximates 0.

The installation according to the invention is plainer than the one usually used heretofore, because a retroaction coil has become useless; it may be ap lied to the generation, reception and amplification of oscillations, more particularly to the reception or amplification of oscillations of high or low frequency and ofi'ers in some cases the advantage of an easier adjustment than the usual retroaction circuit arrangements.

That the installation illustrated is very suitable for the amplification of oscillations of low frequency may appear from which follows If tension fluctuations occur at the primary coil 9 of the transformer they are transmitted to the secondary coil 8 so that consequently, for example, the tension at the grid 4 decreases a little. This decrease of the tension at the controlling grid, the tension of which is equal to or a little lower than that of the cathode 2, causes an increase of the current in the foregrid circuit (see Figure 2).

The loss of tension in the resistance 10 increases now and this causes a decrease of the tension of the two grids. As however the tension decrease at the controlling grid has a greater influence on the foregrid current than the tension fluctuation at the foregrid, (the latter is in phase with the foregrid current fluctuations and exerts therefore an influence are/sea opposite to the one of the controlling grid) the foregrid current keeps increasing even now. This causes again a decrease of the tension of the grids and so on so that a tension fluctuation'at the controlling grid after being amplified is transmitted to the foregrid circuit. As the anode current decreases in about the same measure as the foregrid current increases (see Figure 2), the oscillations of the controlling grid circuit are therefore also transmitted in an amplified manner to the anode circuit in which the telephone 12 has been put.

The amplifying is limited on account of the total current which leaves the cathode, being able to rise only to acertain value, namely, to the saturation current.

sistance characteristic, a plate circuit comrlsin a source of positive plate potentlal, a

' OK 'IICl circuit com risin said source of By a proper choice of the value of the resistance 10 the amplification may be. facilitated, for the resistance 10 is opposite to the negative resistance occurring in the foregrid controlling grid.

anode, cathode, two grids and a negative"-re The resistance 10 is preferably free of induction as otherwise the current fluctuations in the foregrid circuit are not accurately in phase with the tension fluctuations at the controlling grid.

T'Vhat I claim is:

1. A discharge tube relay having a cathode, plate and two grids, a plate circuit comprising a source of positive plate potential, a foregrid circuit comprising said source of plate potential and a resistance, and a control grid circuit comprising said source of plate potential, said resistance, a source of negative potential, and aninput means.

2. A discharge tube relay having a cathode, plate and two grids, a plate circuit comprising a source of positive plate potential, 3, fore I grid circuit comprising a resistance and a source of potential substantially equal to that of the plate, and a control grid circuit comprising said source of foregrid potential, said resistance, a source of negative'potential, and an input means.

3. A discharge tube relay having a cathode, plate and two grids, a plate circuit comprising a source of positive plate potential, a foregrid circuit. comprising said source of plate potential and an adjustable resistance, and a control grid circuit comprising said source of plate potential, said resistance, a source of negative potential, and an input means.

' 4.111 a discharge tube relay having an 

